Here is my response to the Dec. 5 letter by Dunkirk residents Donald J. Koestler and Andrew H. Jazwinski (hereafter, for brevity, K&J) [“Don’t jump to conclusions about climate change,” The Calvert Recorder], a letter which, while agreeing that climates have been warming, strongly disputes the role of increasing greenhouse gases as cause. Their letter was a response to my own letter [“Climate change skeptics cannot deny science,” Nov. 9, The Calvert Recorder], in which I challenged “climate science deniers.” My submission was necessarily simplified, and then further edited down in size by The Recorder. I tried to distill for readers the following basic message from decades of research by thousands of scientists from many nations: Anthropogenic (human-generated) greenhouse gas emissions are a primary, or perhaps the only, reason for the observed warming of the last 150, particularly the last 40, years.

If K&J had read my letter carefully, they would not have claimed that I doubt there are other ways that could cause the earth to warm. In fact, with co-author Mary Parrish of the Smithsonian Institution, I recently published the only climate-related paper of my career. Part of this paper (in peer-reviewed journal Palaeogeography, Palaeoclimatology, Palaeoecology, volume 323-5, 2012) suggests that several sediment layers exposed in our own Calvert Cliffs offer a local record of the so-called “Middle Miocene Climate Optimum,” about 15 to 16 million years ago, and that this warming was possibly caused by increased volcanic emissions of carbon dioxide.

Cosmic rays, which K&J suggest are a viable alternative cause for the observed global warming, remain at best a wild card. First hypothesized in 1959 as a mechanism for climate change, cosmic ray flux is postulated to affect cloudiness. Times of fewer cosmic rays would mean less cloudiness, more sunlight reaching the earth and a warmer atmosphere. Unfortunately for K&J, the recent comprehensive review in a peer-reviewed journal (Laken, B.A., and others, 2012, Journal of Space Weather and Space Climate, volume 2, A18) concludes, “It is clear that there is no robust evidence of a widespread link between cosmic ray flux and clouds … despite over 35 years of constant satellite-based measurements of cloud.”

The so-called “Medieval Warm Period” (MWP), peaking about from the years 950 to 1250, was indeed, as K&J say, warmer than during much of the 20th century, at least in eastern North America and Europe. However, it is not known how “global” the MWP actually was, and in any case, it was probably not as warm as the last several decades have been, contrary to K&J. But increased solar activity and decreased volcanism likely caused it. The fact that “natural” processes can also affect climate change does not by itself prove that the modern climate warming is solely or even partly due to such processes.

To support their position, K&J cite several books, by authors Joseph Bast (president of the Heartland Institute), Steve Goreham (engineer and business executive) and Andrew W. Montford (accountant). None of these authors are scientists, and I could find no peer-reviewed climate-related publications by them in Google Scholar. K&J cherry-picked climate science denier books by non-specialists because the messages in these books fit their opinions. Speaking from my own experience as a publishing scientist, I can say that almost anything can be published as “factual” in books because the manuscripts are seldom subject to peer review prior to publication and are, therefore, rarely cited in technical literature.

K&J choose to ignore the vast, technical, peer-reviewed literature on greenhouse gas emissions’ role in climate change. This is the central failing of their letter. Getting a research paper past critical and often anonymous reviewers is not a piece of cake, as I can attest both as author and reviewer; getting a grant funded is, if anything, even harder (typically, at least 75 percent of good proposals are rejected). Ironically, I suspect the National Science Foundation is urged by politicians to fund more climate science (at the expense of other valuable science) precisely because of doubting Thomases like K&J. Soft-money research funding is so tenuous some excellent scientists don’t try for it, having families to support. Incidentally, what K&J say about grant-hungry university scientists applies largely to the U.S.: The many foreign climate scientists are mostly salaried professionals.

As for the money issue, the carbon-fuel extraction, refinement and utilization industries naturally fear the consequences to their industries, should the world undertake to reduce rates of greenhouse gas emissions. Thus, there seem to be plenty of incentives for institutes and politicians to dispute anthropogenic warming.

Before cherry-picking non-peer-reviewed books to support their position, climate science deniers should consult SkepticalScience.com and realclimate.org. It may also help to peruse a college-level textbook on climate, and I recommend “Earth’s Climate: Past and Future,” 2008.

In summary, K&J gave me no reason to retract anything I wrote in my Nov. 9 letter to this paper. If K&J “have followed this subject for more than 30 years,” they should acknowledge that many of the initial skeptics have come around to accepting global warming and the role of greenhouse gas emissions (e.g., economist Bjoern Lomborg in 2010 and Berkley physicist Richard Muller in 2011), and that computer simulations made 10 to 20 years ago have proven close to what has happened. If anything, the model predictions incorporating known and predicted greenhouse gas concentrations have underestimated the rate of Arctic sea ice decline and the accelerated loss of mass from the Greenland ice sheet.